The present invention relates to a deflection yoke for a cathode-ray tube and a vertical deflection coil winding method of the deflection yoke, and more particularly to the winding of the vertical deflection coil mounted on the cone portion of the cathode-ray tube, for deflecting an electron beam emitted from an electron gun.
As shown in FIG. 1, a cathode-ray tube (CRT) 1 includes a panel 3 on the inside surface of which a fluorescent film 2 is formed, an electron gun 4 housed within the neck portion of the CRT, and a deflection yoke 5 established on a funnel 6 which is coupled to panel 3. An electron beam is selectively deflected by means of deflection yoke 5 according to the beam's scanning position against fluorescent film 2. The deflected beam is landed on fluorescent film 2 to form a picture. In CRT 1 constructed as above, in order to properly deflect the electron beam emitted from electron gun 4 mounted on the neck portion of funnel 6, the horizontal deflection coil of deflection yoke 5 needs to form a pincushion-shaped deflection magnetic field, and the vertical deflection coil of deflection yoke 5 needs a barrel-shaped deflection magnetic field. One embodiment of the deflection yoke is shown in FIG. 2.
The deflection yoke 10 includes a cone-shaped separator 11, a horizontal deflection coil 12 established on the inner circumferential surface of separator 11, a core 13 established on the outer circumferential surface of separator 11, and a vertical deflection coil 14 wound on core 13.
In deflection yoke 10 constructed as above, since the distribution of the pincushion-shaped magnetic field formed by means of vertical deflection coil 14 according to the winding method of the coil wound on core 13 is different from the distribution of the barrel-shaped magnetic field formed by means of vertical deflection coil 14 according to the winding method of horizontal deflection coil 12, the distortion of the magnetic field due to the deflection of the electron beam is generated. Numerous coil winding methods have been proposed in order to compensate for this deflection distortion.
In one such vertical deflection coil winding method, after one winding layer is made by winding wire from one end of the core to the other end thereof, and returning back to the one end of the core, the next wire winding layer is formed by repeating the above process. In such a winding method, the winding of wire is returned to the start point of the first winding by a "shootback" method in which the wire follows a straight path along the outer circumferential surface of the core, or by a "spiralback" method in which the wire follows an annular path the interval of which becomes enlarged gradually on the outside circumferential of the core.
If the shootback method is used, the wire slips in the neighborhood of the vertical end of a winding layer and the position of the wire may deviate from the winding layer due to the sudden change of a wire position. To solve such a problem, adhesive means is needed to maintain the original position of the wire.
Since the part of return winding is arranged along the inner side of the core, an effective region, the spiral winding method introduces an unnecessary high frequency to the deflection magnetic field and generates an undesirable ringing phenomenon. Namely, an indirect magnetic field which adversely affects the function of the deflection yoke is generated. Also, when the coil wound on the core returns back from one side to the other side of the core, the wire may be twisted.
In the spiralback winding method, as shown in FIG. 3, a main winding 22 is wound repeatedly from side to side in order to minimize the indirect magnetic field, and a wire 23 returns back at once from one side of core 21 to the other side thereof was developed.
However, such a winding method has a drawback that a magnetic field distribution by main winding 22 wound from the left end to the right end of the core does not generate the distortion of the magnetic field, but wire 23 returning back to the start point at once generates the distortion of the magnetic field.
FIG. 4 shows another embodiment among the winding method of the vertical deflection coil. Here, a fixing frame 33 on which a plurality of slit 32 which are spaced mutually a predetermined distance on the bottom portion of a core 31, and on which the wire is supported, are formed, is mounted to core 31. A wire 34 forming the coil wound on one quadrant of core 31 is wound clockwise. Then, wire 34 is wound counterclockwise from an adjacent quadrant of the core.
While the deflection yoke on which the coil is wound can reduce physical spreading of the spot of the electron beam landed on a fluorescent surface by the above method, fixing frame 33 needs to be established on the lower portion of the core. This increases the production cost of the deflection yoke and lowers productivity by marking the winding of wire 34 difficult.